Increase disk partition size when windows disk manager has extend disk grayed out

Firstly, extend volume with Diskpart.exe

To extend volume with diskpart.exe, you just need to open up Command line utility with Administrators rights (Start -> right click CMD and choose run as administrator). Type Diskpart and the utility fires up.

  1. Open a command prompt and type diskpart.
  2. At the DISKPART prompt, type list volume. Make note of the basic volume you want to extend.
  3. At the DISKPART prompt, type select volume <volumenumber>. This selects the basic volume volumenumber that you want to extend into contiguous, empty space on the same disk.
  4. At the DISKPART prompt, type extend [size=<size>]. This extends the selected volume by size megabytes (MB).

Moreover, you can use this commands like: Delete partition, Format and more – you can read further on over here.